It is known that owing to the influence of chemical substances used for hair coloring or perming, or influence of heat upon hair blowing, hair system shrinks and many voids appear inside of the hair to cause drooping of the hair (e.g., refer to Non-patent document 1). Such damaged hair has poor elasticity, becomes excessively dry, cannot recover easily from a change in its shape such as a cow-lick or has poor manageability. At present, rinse-off hair cosmetic compositions contain an oil or fat, silicone, polymer or the like in order to prevent the hair from excessive drying, provide moist feel to the hair and improve hair smoothness. These compositions can provide temporal countermeasure by adhesion of such a component onto the hair, but cannot fundamentally improve the above-described troubles.
A hair cosmetic composition using an organic acid in combination with a specific organic solvent is known as those capable of improving hair quality, protecting the hair from excessive drying and providing the hair with manageability and luster (refer to Patent documents 1 and 2). The effects brought by a combination of only one kind of organic acid and the organic solvent, however, have not been satisfactory.    Non-patent document 1: Fragrance Journal, No. 6, p. 11(2000)    Patent document 1: JP-A-2002-47142    Patent document 2: JP-A-2002-29938